lua/streaming: provide streaming buffer as argument

lua/streaming: provide streaming buffer as argument

When setting up a Lua output script for streaming data, we're
explicitly requesting stream data. Just pass the streaming data as
arguments, rather than requiring the script to make an extra call to
get the stream data.

The streaming data will be passed in the "stream" field of the args
passed to the log function.

Eliminates the SCStreamingBuffer Lua function.